材料期刊网

测定钢中低含量硫时,空白校正一直是个难题.电感耦合等离子体原子发射光谱法(ICP-AES)测定硫的检出限可达0.02 mg/L,据此计算,硫的测定下限可达0.000 5%.为实现钢中质量分数大于0.000 5%硫的测定,进行了钢在盐酸、硝酸和高氯酸中的溶解试验和ICP-AES测定钢中硫的空白研究.发现了纯试剂空白值比铁基空白值高约0.002%(质量分数)的反常现象.并对铁基背景和背景扣除方式进行了研究.结果表明,铁基体的背景强度和背景强度的标准偏差比纯试剂和水高,高强度的铁基体背景湮灭了部分测量峰,导致了上述反常现象.铁基背景标准偏差的增大,导致了分析方法的测定下限上升.因此,应尽量选择多相元平均背景.提出了先用盐酸溶解样品除去纯铁基体中的硫,后加硝酸和高氯酸制备无硫铁基空白试液.样品分析减去无硫铁基空白才能正确的分析结果.按照实验方法测定钢样中质量分数小于0.01%的硫,结果的相对标准偏差(RSD,n=5)小于10%,测定结果与红外分析吸收法一致.

The blank correction was a challenge during determination of low content sulfur in steel.The detection limit of sulfur was low to 0.02 mg/L in determination by inductively coupled plasma atomic emission spectrometry(ICP-AES).According to this, the lower determination of sulfur was 0.000 5%.In order to realize the determination of sulfur in steel with content higher than 0.000 5%, the dissolution tests of steel in hydrochloric acid, nitric acid and perchloric acid were conducted.The blank during determination of sulfur in steel by ICP-AES was studied.It was found that the blank value of pure reagent was about 0.002% (mass fraction) higher than that of iron-based sample.The background and its deduction method of iron matrix were investigated.The results showed that the background intensity of iron matrix and the standard deviation of background intensity were higher than those of pure reagent and water.Partial measurement peak was annihilated by the high-intensity background of iron matrix, leading to the abnormal phenomenon above.The low limit of determination of analytical method increased due to the increase of standard deviation of iron matrix background.Therefore, the average background of multi-phases should be selected for correction.The sulfur in pure iron matrix sample was firstly removed by dissolution using hydrochloric acid.Then the sulfur-free iron matrix blank solution was prepared by adding nitric acid and perchloric acid.The accurate analysis results could be obtained by subtracting the sulfur-free iron matrix blank from sample.The proposed method was applied to the determination of sulfur in steel sample with mass fraction less than 0.01%.The relative standard deviation (RSD, n=5) was less than 10%.The found results were consistent with those obtained by infrared absorption analysis.